This invention relates to a wedge-type brake actuator and more particularly to an improved wedge and roller type brake actuator.
A wedge or wedge and roller type actuator is employed frequently in drum-type brakes. Such a wedge-type actuator includes an actuating wedge that operate to urge a pair of rollers that are slidably and rotatably supported within a cage into engagement with a brake shoe or other element which engages the brake shoe for urging the brake shoes into actuating engagement with an associated brake drum. This type of actuator has many advantages and can significantly reduce operating loads due to the use of the interposed rollers and the associated mechanism. However, it is sometimes possible for circumstances to arise in which the wedge, which has the inclined surfaces that engage with the rollers, passes beyond the rollers. Furthermore, it is desirable to maintain the timing relationship between the wedge and rollers and such push through can result from the loss of this relationship.
It is, therefore, a principal object of this invention to provide an improved wedge-type actuator for brakes.
It is a further object of this invention to provide a wedge-type brake actuator that will avoid the possibility of push through where the rollers move past the inclined wedge surface and onto the wedge shank.
In accordance with the invention, an arrangement is provided for limiting the degree of relative movement between the wedge actuator and the roller carrying cage. This arrangement can effectively prevent push through. However, when such a positive stop is provided to limit the relative movement, there can arise a risk that the forces encountered will be unduly high and can damage the mechanism due to the mechanical advantage between the rollers and the inclined wedge surface.
It is, therefore, a further object of this invention to provide an improved stop mechanism for a wedge-type actuator that will eliminate push through without loading the cage and rollers to a degree not tolerable by typical existing embodiments.